Brakes of the type referred to at the beginning are disclosed, for example, by EP 694 707 B3. A characteristic feature of the brakes according to the state of the art is the axial offset of the hold-down yoke by way of an eccentric interlocking support in the brake caliper, in order to exert not only the radial but also a tangential pretensioning on the brake linings via the positively interlocking engagement in the hold-down springs specially formed for this purpose.
The basic principle of radial and tangential pretensioning has proved its worth and should be retained. According to the invention, however, design and functional modifications are made to the brake caliper and to the relevant parts of the hold-down system, in order to afford greater efficiency and greater versatility.
FIGS. 1 and 2 show the brake according to EP 694 707 B3. Here FIG. 1 shows a brake lining 11, which is guided and supported radially inwards and on both sides in a circumferential direction in a channel guide of the brake caliper or back plate assembly, and on the radially outer edge of which lining a hold-down spring is supported, which is symmetrically formed to both sides of its center axis. Centrally, the hold-down spring comprises a radially deeper center area 3, from which the higher spring legs 6, 7 extend outwards on both sides along the outer edge of the lining, in order for the ends to then exert a spring action on the brake lining when a likewise symmetrically formed hold-down yoke 1 engages with a positive interlock in the here radially inward formed center area.
The hold-down yoke 1 is formed from round material. The spring pretensioning occurs when the hold-down yoke 1, as in FIG. 2, is anchored on the actuation side in interlock openings of the brake caliper, and on the other side is then fixed firmly but detachably by means of bolts to a bearing block of the brake caliper on the wheel-rim side. The hold-down yoke extends over a caliper opening serving for the fitting/removal of brake linings, supported on both sides of the brake disc, and in a direction towards the brake or center axis A.
In the axial direction of the brake linings, the hold-down springs are coupled to the brake lining, because radial shoulders 12, 14 of the outer edge of the brake lining pass through elongated openings 8, 9, 10 in the spring. At the ends, the spring legs bear against further radial shoulders 13, 13 of the outer edge of the brake lining. The hold-down springs are embodied as leaf springs.
The radial and tangential pretensioning acting on the brake lining by means of the hold-down spring is generated, according to the state of the art, in that the hold-down yoke 1 engages with a positive interlock in the radially formed center area 3 of the hold-down spring and in turn is supported by positive interlock in actuation and wheel rim-side anchorages of the brake caliper, always offset towards the brake disc run-out side by an axial offset x relative to the center or brake axis A, in the direction of rotation of the brake disc in forwards travel. As a result, the corresponding spring leg is also forced in a tangential direction. For the eccentric positively interlocking support of the hold-down yoke 1, the requisite design shapes must be provided at corresponding positions in the brake caliper casting, and these design shapes then still have to undergo machining operations. The bearing points for the hold-down yoke 1 are therefore formed asymmetrically on/in the brake caliper.
The relevant brakes are fitted on both sides of the axle, so that they too need to be of mirror-symmetrical design. This means that for brake calipers according to the state of the art different casting pattern designs are required for a left-hand brake and a right-hand brake, in order to produce the asymmetrical support and holding areas. Accordingly, the positions of the subsequent machining operation for the support and holding areas in the case of a left-hand brake are different from those in that of a right-hand brake.
Owing to the aforementioned asymmetry, this principle with different caliper designs is an obstacle to economic and cost-efficient production of the brake calipers mass-produced by casting and machining.
The object of the invention, therefore, is to develop the brake according to EP 694 707 B3 in such a way that said disadvantages are eliminated. In particular, the object of the invention is to manufacture the caliper disc brake of the type specified at the beginning in a more efficient and more versatile manner.
According to the invention the stated object is achieved in a caliper disc brake of the aforementioned type in that the tangential pretensioning is at least partially attributable to the fact that the dimensions of the hold-down device, measured in a tangential direction from the centerline, are at least in parts greater on the disc run-out side than on the disc run-in side.
Here the invention is based on the finding that the holding device for the hold-down device or in other words the support areas for a hold-down yoke on the caliper can be designed symmetrically if the tangential pretensioning of the hold-down spring originates not from an asymmetry of the caliper, but rather an asymmetry of the hold-down device.
The advantages are thereby obvious, since the brake calipers of mirror-symmetrical design in the holding and support areas for the hold-down device on each axle in this respect no longer require different molds to form the casting design shape. Furthermore, the subsequent machining can be standardized.
According to the invention, the hold-down spring preferably lies on the actuation side. Specifically, according to the invention, it is preferable for the hold-down spring which holds down the brake lining lying on the actuation side and/or the pressure plate likewise lying on the actuation side, but not the hold-down spring which holds down the brake lining on the wheel rim side, to be pretensioned in the tangential direction. In this way, mechanically adverse moments are avoided.
According to the invention, it is furthermore preferably provided that the hold-down device bears, to generate the radial pretension, by way of a first region and, to generate the tangential pretension, by way of a second region, against the hold-down spring, and the spacing of the central point of the first region from the central point of the second region is smaller in the radial direction than in the tangential direction. In this way, the hold-down spring is considerably mechanically relieved of load, because in this way, regions of force introduction into the hold-down spring are remote from the regions of maximum bending load.
According to the invention, the first region is furthermore preferably formed on a radially inwardly extending bead. Inter alia, the advantages already mentioned above are attained in this way.
According to the invention, the second region is furthermore preferably oriented obliquely with respect to a radial plane containing the centerline. In this way, slight relative movements (sliding) during reversing movements of the hold-down spring are possible. This relieves the hold-down spring of load in critical zones.
In addition to the caliper disc brake described above, the invention also provides a hold-down device, in particular of a caliper disc brake of said type. According to the invention, the dimensions of the hold-down device, measured in a tangential direction from a centerline of a holding device which holds the hold-down device on a brake caliper of a caliper disc brake, are at least in parts greater on the disc run-out side than on the disc run-in side.
A hold-down device of said type is suitable for generating the tangential pretension, discussed above in detail, even when the holding device formed on the brake caliper for holding and supporting the hold-down device is symmetrical in relation to a radial plane containing the centerline, such that in this respect, there is no need for different casting moulds for a right-hand brake, on the one hand, and for a left-hand brake, on the other hand.
According to the invention, the hold-down device preferably has a projection which extends in the tangential direction and which lies on the disc run-out side and in the actuation-side region. In this way, in accordance with the statements made above, the desired tangential pretension can be generated on the actuation side, wherein such tangential pretension is avoided on the wheel-rim side.
As already mentioned above, according to the invention, the hold-down device preferably has a radially inwardly extending bead.
In a further preferred embodiment of the invention, a recess is provided in the direction of the axis of rotation, the side flanks of which recess, in interaction with the holding device, serve for the transmission of tangential forces. In this way, a mechanically particularly simple solution for the generation of the tangential pretension is realized.
According to the invention, the indentation is furthermore preferably symmetrical in relation to a radial plane containing the centerline. In this way, it is also possible for the holding device to be of symmetrical design on the brake caliper, which yields the advantages already mentioned above.
According to the invention, the recess furthermore preferably lies on the actuation side.
In a further preferred embodiment of the invention, a coding device is provided. The coding device furthermore preferably has a recess.
In a particularly preferred embodiment of the invention, the coding device lies on the wheel-rim side.